He is the eldest son of the Mad King, Aerys II. Prince Rhaegar Targaryen is the son of King Aerys Targaryen and Queen Rhaella Targaryen, making him Daenerys and Viserys’s older brother (though Dany was born after his death).

He marries a Dornish princess and has two children, who are later murdered by The Mountain. Rhaegar and Princess Elia Martell (Oberyn Martell’s sister, FYI) of Dorne have a daughter, Rhaenys, and a son, Aegon. The children are killed, and then Ser Gregor Clegane rapes Elia before stabbing her to death with a sword. Makes sense why Oberyn wanted to kill him so bad, huh?

He allegedly abducts Lyanna Stark, which ignites the deadly rebellion against the Targaryens. Despite a seemingly happy marriage to Princess Elia, Rhaegar “abducts” Ned’s sister for undisclosed reasons. When the Starks order Rhaegar to release Lyanna, the Mad King has both Ned’s father, Rickard, and oldest brother, Brandon, cruelly executed. This prompts Ned and Robert Baratheon (who was betrothed to Lyanna at the time) to team up with several other clans to take down the Targaryens. As we discover later on, Lyanna and Rhaegar were actually genuinely in love and ran off together on purpose. The Starks and Baratheons likely used the kidnapping story to explain away why Lyanna ran off with the Mad King’s son (instead of admitting the truth and bringing shame to their Houses).

He dies at the end of Robert Baratheon’s hammer. Although Rhaegar manages to avoid the initial uprising while living in Dorne, he’s eventually summoned to battle. During a fight known as the Battle of the Trident, Rhaegar goes up against Robert, who deals him a fatal blow with his war hammer.

He has been mentioned in the show many times before. In the first episode of season one, Robert and Ned share an emotionally charged moment in the crypt where Lyanna is buried, where Robert reveals that “he kills [Rhaegar] every night” in his dreams. In season three, Jorah Mormont and Ser Barristan Selmy bicker over how honorable Rhaegar truly was in front of Daenerys, and Barristan brings him up again in season five when he shares some pleasant memories of Rhaegar’s love of singing. Petyr Baelish also recounts the events surrounding Rhaegar’s kidnapping of Lyanna to Sansa Stark in the same crypt where Robert and Ned were years earlier. And of course, Daenerys has been bringing him up in season seven — including to Jon Snow, who still doesn’t know that’s his dad.

He’s Jon Snow’s father. By far the most significant point of Rhaegar’s role in the current state of Westeros is his parentage of Jon Snow. In the season-six finale, Bran travels back in time, once again, to the Tower of Joy, where Lyanna is being held captive, according to the Starks and the Baratheons. Ned arrives to rescue his dying sister, who reveals she is the mother of Jon Snow and begs Ned to raise the baby as his own. Although she doesn’t explicitly say Jon is Rhaegar’s son onscreen, HBO confirmed the news with a handy infographic explaining how all the characters are related. This whole scene also feeds into the myth of the “Prince That Was Promised.”

More importantly, he’s Jon Snow’s legitimate father. Following the Tower of Joy revelation in season six, season seven’s fifth episode, “Eastwatch,” casually lets everyone in on a huge secret: JON SNOW ISN’T ACTUALLY A BASTARD. While paging through a book at the Citadel, Gilly reads an old maester’s record of an annulment between Rhaegar Targaryen and his wife and the new marriage that the maester officiated for Rhaegar afterwards. In other words, Rhaegar annulled his vows to Elia Martell and properly married Lyanna Stark before she gave birth to Jon, which means he’s not a bastard at all. Jon is the rightful heir to the Iron Throne, even more so than Daenerys Targaryen.